Firearm receivers that utilize a magazine designed for Ruger model 10/22 firearms all have dimensional differences in the area where the magazine mates with the receiver. Even firearms from the same manufacturer of the same model designation have differences in the receiver dimensions. As a result, existing available magazines have had to be manufactured with sufficiently loose fits to enable them to try to fit as many combinations of receivers as possible, with the accompanying result that they do not fit any one receiver very well, to the performance detriment of the firearm.
Function of a firearm is directly related to the fit of the magazine in the receiver, so loose fitting magazines may cause unreliable firearm functioning. On the other hand, the more exactly the magazine fits the firearm receiver, the more reliable the function of the firearm can be expected to be. This is in conflict with the need to manufacture loose fitting magazines to ensure insertability in receivers that are of varying tolerances from the manufacture's intended optimal design specification.
In addition, even if all receivers were manufactured to dimensional perfection manufacturing variations in magazines may generate unreliability. Further, different brands and lots of ammunition may require different dimensional relationships between a magazine and the receiver.
There is a need for a magazine that fits into a wide range or receiver tolerances, with reliable function in each.
The present invention overcomes the limitations of the prior art by providing a magazine for a firearm having a magazine well that has a body with the chamber for receiving ammunition. The body has an upper opening to the chamber, and has a contact portion with adjustable screws that contact a surface in the magazine well. Adjustment of the screws is used to establish a precise selected position of the magazine with respect to the receiver, permitting adjustment of the feed height, feed angle and ejector angle. Four screws are provided, one at each corner of the upper surface of the magazine.